Scientists who wondered why human skin still boasts as many follicles as that of great apes—ours, of course, grow hair much, much finer—believe our species' continued hairiness serves as an alarm system that protects us from bedbugs and other biting insects, the Economist finds. The researchers, who shaved a patch of arm hair from 29 volunteers and released hungry bedbugs there and on an unshaved patch, found that their subjects detected the insects' movement much faster when hair was involved—recording it every four seconds, versus every 10—and that the fine hairs slowed down the bugs' feeding.
"Our findings show that more body hairs mean better detection of parasites—the hairs have nerves attached to them and provide us with the ability to detect displacement," the lead researchers says, speculating that humankind's loss of thicker fur may have been evolution's way of depriving parasites of hiding places. "We retain the fine covering because it aids detection and if we lost all hair, even the relatively invisible fine hair, our detection ability goes right down." (Read more bedbugs stories.)